1. Field of the Invention
The present invention relates to a charged beam apparatus using a charged beam such as an electron beam or ion beam, including a lithography device for applying intricate beam fabrication on a sample to be worked, or for forming a fine pattern on the substrate of a semiconductor, or a sample analyzer for analyzing and assessing samples.
2. Description of the Prior Art
In processing technologies using a charged beam, intended for applying a fine electronic circuit pattern to the substrate of a semiconductor, or for applying fine beam fabrication on a sample to be worked, charged beam devices with a built-in sample moving mechanism capable of highly accurate beam and sample position control are essential. Upgraded performance and function are vital for these charged beam devices, because they govern the characteristics of samples prepared.
A charged beam apparatus requiring an ultra-high vacuum sample chamber adopts a method which mounts an aperture with a tiny hole diameter at the interface between the sample chamber and a high-vacuum charged beam optical column to perform differential venting. With such a conventional apparatus, vacuum characteristics differ according to the structures, materials, gas release characteristics, surface treatment techniques, etc. of or for the various functional devices incorporated in the ultra-high vacuum chamber. Hence, it is difficult to achieve both an ultra-high vacuum and high performance in a complicated, highly accurate moving mechanism incorporated in the vacuum chamber.
For the realization of an ultra-high vacuum of 10.sup.-7 Pa or less, in particular, it is indispensable to reduce the surface areas of the structures within the chamber as well as the internal surfaces of the chamber. For this purpose, it is crucial to planish or surface-treat the internal surfaces of the chamber or the surfaces of the structures and to constitute these structures and internal surfaces from materials involving minimal gas release.
Normally, the moving mechanism uses a sliding guide or a rolling guide, and thus inevitably requires a lubricant for the guide surface. However, a lubricant entails gas release under a vacuum and is far from satisfactory, thus making its use in an ultra-high vacuum difficult. A non-lubricating moving mechanism with a coating or the like, on the other hand, causes a stick-slip under an ultra-high vacuum, making precision driving difficult. In order to attain an ultra-high vacuum, moreover, moisture adsorbed onto the surfaces of the structures within the chamber must be evaporated and exhausted, making a bake at about 120.degree.-200.degree. C. essential. All of this poses difficulty in using a high-accuracy moving mechanism under an ultra-high vacuum.
In a semiconductor lithography apparatus with strict requirements for fine fabrication and high accuracy, in particular, a highly stable, highly accurate laser interference comparator system is incorporated for real-time management of the sample position and the positional coordinate of the illuminating beam. A mirror as a reference and an interferometer that are used with such an apparatus have their inherent temperature coefficients, and are sensitive to temperature changes. Thus, baking which greatly changes the ambient temperature is a major factor to induce decline in the comparator accuracy. An electron beam writing device and a focused ion beam device have a built-in XY stage for making a high-accuracy sample movement. However, this XY stage poses the problem, in vacuum evacuation, of an increased surface area ascribed to its complicated structure. Moreover, gas release due to the vaporization of a lubricating oil used for a rolling bearing, etc. makes the use of these devices under an ultra-high vacuum difficult.
With gas-assisted etching or deposition with a charged beam, a gas, such as active chlorinous gas or organometallic gas, is introduced into the chamber, thus posing the problem of whether the internal surfaces of the chamber and structures incorporated in the chamber are corrosion resistant or not.
As described above, much difficulty is involved in using conventional techniques to achieve an ultra-high vacuum and the use of a sample chamber and an optical column resistant to corrosive gas in the vicinity of an ordinary high vacuum portion.
FIG. 1 shows the structure of an electron beam writing device, an example of the charged beam apparatus according to conventional technology. In the drawing, the reference numeral 1 denotes an electron-optical column constituting an electron beam optical system. The numeral 11 is an electron gun for generating a high-intensity electron beam. The numerals 12, 13, 14 are each an electron lens for focusing the electron beam into a desired shape. The numeral 15 is a blanking system for ON-OFF control of the electron beam. The numeral 16 is a deflector for deflecting and scanning the electron beam. The numerals 17, 18 are each a pump for venting the electron-optical column to a vacuum.
Furthermore, the numeral 2 is a sample chamber for accommodating a substrate to be worked. The numeral 21 is a holder for holding a sample in place. The numeral 22 is a sample moving mechanism for moving the sample to a desired position. The numeral 23 is a laser interference mirror which serves as a reference for measuring the sample position or beam position. The numeral 24 is a laser interferometer. The numeral 25 is a wavelength stabilizing laser. The numeral 26 is a receiver for laser interference measurement. The numeral 27 is a motor for driving the sample stage from outside the vacuum. The numeral 28 is a vacuum venting pump for the sample chamber. This structural diagram omits an illustration of a chamber for sample replacement.
Compared with a conventional electron beam writing technique which writes a fine pattern on an organic resist to form a mask pattern, patterning on an inorganic resist enables finer pattern formation and purer treatment. With such patterning on an inorganic resist, a cleaning technique for preventing contamination due to oxidation or gas adsorption of the surface of the substrate to be worked becomes important. In this unprecedented aspect, development of a lithographic technology employed under an ultra-high vacuum is of importance. In gas-assisted etching or deposition with a charged beam, devices provided with an anti-corrosion measure for the chamber and structures incorporated therein are indispensable for pattern formation on the clean surface by introduction of an active chlorinous gas or an organometallic gas.